1. Field of the Invention
The present invention relates to a tape tension control device for a video cassette tape recorder (hereinafter "VCR") and more particularly, to a tape tension control device for a VCR which enables the tensional force applied to a tape to be controlled even in a review (hereinafter "Rev") mode.
2. Description of the Prior Art
Several types of tape tension control devices for a VCR are well known in the art. One of such tape tension control devices for a VCR is illustrated in FIG. 1 which shows a conventional tape tension control device for a VCR. As shown in FIG. 1, the conventional device for a VCR is structured with a roller 10, a tension arm 2 having a tension post 2a, a projecting piece 2b, a projection 2c and a band fixing hole 2d, and rotatably mounted with an axial pin 3 disposed at the outer side of a reel table 1, a band fixing member 5 to which one end of a band 4 wound around the reel table 1 is fixed, and mounted to the band fixing hole 2d, an elongated hole 6a through which a band fixing member 6 is fixed with a screw 7 and formed at the other end of the band 4, a hooking projection 2e formed at the lower portion of the tension arm 2 resiliently supported by a tensional coil spring 8, and a plate 9 provided with a hooking projection 9a and a projecting piece 9b which are connected to or disconnected from the projecting piece 2b and the projection 2c of the tension arm 2, and mounted at the lower side of the tension arm 2.
In such conventional device as shown in FIG. 1, when the tensional force applied to a tape T becomes larger during the tape running in a play mode, the tension arm 2 rotates clockwise about the axial pin 3 by overcoming the moment of the tensional coil spring 8 and, at this time, the band 4 wound around the reel table 1 is released so that the reel table 1 rotates fast.
On the contrary, in case that the tape tension becomes smaller, since the tension arm 2 is rotated counterclockwise by the spring force of the tensional coil spring 8, the band 4 is closely contacted to the outer peripheral surface of the reel table 1 so that the speed of the rotation of reel table 1 is reduced, thereby maintaining the tensional force of tape constant. Meanwhile, when the tape T is running in a Rev mode, the plate 9 moves to the right and the projecting piece 9b of the plate 9 contacts the projection 2c of the tension arm 2 so that the tension arm 2 rotates clockwise. In this condition, the tape T is released from the tension post 2a as shown in the dotted line of FIG. 1 so as to be run in the friction free state.
However, in such conventional device, there is no problem in a play mode, but since the tape T runs in a state of releasing from the tension post 2a in the review mode, the tape tension cannot be controlled, resulting in the inequality of tape tension. Also, it may cause the tape T to be damaged and thus the picture quality becomes bad. The projecting piece 9b of the plate 9 used in the review mode also impairs the simple structure of the device.